• Values, variables
• Vectors
• Loops
• Logical statements
• Control statements
• Functions

https://scratch.mit.edu/

Microprocessors can only represent two signs (states):

• ‘Off’ = 0
• ‘On’ = 1

• Only two signs: 0, 1.
• Base 2.
• Columns: \(2^0=1\), \(2^1=2\), \(2^2=4\), and so forth.

• Sufficient to represent all natural numbers in the decimal system.

• Sufficient to represent all natural numbers in the decimal system.
• Representing fractions is tricky
  • e.g. \(1/3=0.333..\) actually constitutes an infinite sequence of 0s and 1s.
  • Solution: ‘floating point numbers’ (not 100% accurate)

What is the decimal number 139 in the binary counting frame?

What is the decimal number 139 in the binary counting frame?

• Solution:

\[(1 \times 2^7) + (1 \times 2^3) + (1 \times 2^1) + (1 \times 2^0) = 139.\]

What is the decimal number 139 in the binary counting frame?

• Solution:

\[(1 \times 2^7) + (1 \times 2^3) + (1 \times 2^1) + (1 \times 2^0) = 139.\]

• More precisely:

\[(1 \times 2^7) + (0 \times 2^6) + (0 \times 2^5) + (0 \times 2^4) + (1 \times 2^3)\\ + (0 \times 2^2) + (1 \times 2^1) + (1 \times 2^0) = 139.\]

• That is, the number 139 in the decimal system corresponds to 10001011 in the binary system.

If computers only understand 0 and 1, how can they express decimal numbers like 139?

If computers only understand 0 and 1, how can they express decimal numbers like 139?

• Standards define how symbols, colors, etc are shown on the screen.
• Facilitates interaction with a computer (our keyboards do not only consist of a 0/1 switch).

How can a computer understand text if it only understands 0s and 1s?

A modified version of South Korean Dubeolsik (two-set type) for old hangul letters. (Illustration by Yes0song 2010, Creative Commons Attribution-Share Alike 3.0 Unported)

How can a computer understand text if it only understands 0s and 1s?

• Standards define how 0s and 1s correspond to specific letters/characters of different human languages.
• These standards are usually called character encodings.
• Coded character sets that map unique numbers (in the end in binary coded values) to each character in the set.

How can a computer understand text if it only understands 0s and 1s?

• Standards define how 0s and 1s correspond to specific letters/characters of different human languages.
• These standards are usually called character encodings.
• Coded character sets that map unique numbers (in the end in binary coded values) to each character in the set.
• For example, ASCII (American Standard Code for Information Interchange).

ASCII logo. (public domain).

• In practice, Data Science means handling digital data of all formats and shapes.
  • Diverse sources.
  • Different standards.
  • read/store data.
• At the lowest level, this means understanding/handling encodings.

Two core themes of this course:

1. How can data be stored digitally and be read by/imported to a computer?
2. How can we give instructions to a computer by writing computer code?

Two core themes of this course:

1. How can data be stored digitally and be read by/imported to a computer?
2. How can we give instructions to a computer by writing computer code?

In both of these domains we mainly work with one simple type of document: text files.

• A collection of characters stored in a designated part of the computer memory/hard drive.
• An easy-to-read representation of the underlying information (0s and 1s)!

• A collection of characters stored in a designated part of the computer memory/hard drive.
• An easy to read representation of the underlying information (0s and 1s)!
• Common device to store data:
  • Structured data (tables)
  • Semi-structured data (websites)
  • Unstructured data (plain text)
• Typical device to store computer code.

Install RStudio from here!

Install Atom from here!

Recall the initial example (survey) of this course.

1. Access a website (over the Internet), use keyboard to enter data into a website (a Google sheet in that case).

2. R program accesses the data of the Google sheet (again over the Internet), downloads the data, and loads it into RAM.

3. Data processing: produce output (in the form of statistics/plots), output on screen.